Latex polymers

ABSTRACT

LATEX POLYMERS COMPRISING AN AQUEOUS DISPERSION OF AN INTERPOLYMER SELECTED FROM THE CLASS CONSISTING OF (A) A COPOLYMER OF VINYL ACETATE AND VINYL HYDROLYZABLE SILICONE AND (B) A TERPOLYMER OF VINYL ACETATE, AN ESTER, E.G. ACRYLIC ESTER, MALEIC ESTER OR FUMARATE ESTER, AMD VINYL HYDROLYZABLE SILANE, AS WELL AS THE CROSSLINKED POLYMERS DERIVED THEREFROM; SAID LATEX POLYMERS HAVING UTILITY AS PROTECTIVE SURFACE COATINGS AND AS VEHICLES FOR PAINT FORMULATIONS.

US. Cl. 26029.6 T 11 Claims ABSTRACT OF THE DISCLOSURE Latex polymerscomprising an aqueous dispersion of an interpolymer selected from theclass consisting of (A) a copolymer of vinyl acetate and vinylhydrolyzable silane and (B) a terpolymer of vinyl acetate, an ester,e.g. acrylic ester, maleic ester or fumarate ester, and vinylhydrolyzable silane, as well as the crosslinked polymers derivedtherefrom; said latex polymers having utility as protective surfacecoatings and as vehicles for paint formulations.

This is a divisional application of US. application Ser. No. 23,992,filed Mar. 30, 1970, now US. Pat. No. 3,729,438.

BACKGROUND OF THE INVENTION This invention relates to novel latexpolymers and to the novel cross-linked polymers derived therefrom. Moreparticularly this invention relates to novel silane latex polymers whichpolymerize into clear, stable crosslinked polymers merely upon dryingand the elimination of water.

The term latex polymer has a meaning well known in the art and is usedto designate an aqueous dispersion of a water-insoluble polymer which ispresent in the form of very fine particles. Latex polymers are oftenreferred to as polymer or interpolymer latices, or aqueous emulsionpolymers.

Latex polymers are well known in the art and have found wide utility asvehicles in the preparation of surface coating compositions. Forinstance they are often employed as adhesives and as film forming agentsin paint compositions designated for all types of application andexposure. 1

SUMMARY OF THE INVENTION Therefore it is an object of this invention toprovide silane latex polymers suitable for use in the field of surfacecoatings. A further object of this invention is to provide cross-linkedpolymers derived from said latex polymers suitable for use as a coatingprotective for a substrate. Other objects and advantages of thisinvention will become readily apparent from the following descriptionand appended claims.

More specifically the latex polymers of this invention are film-formingcompositions comprising an aqueous dispersion of a water insolubleinterpolymer consisting essentially of (a) a vinyl hydrolyzable silaneand (b) an ester selected fromthe class consisting of acrylic esters,maleic esters and fumaric esters, and/or. (c) vinyl acetate. Uponremoval of the Water from said latex polymer, the interpolymer thereinfurther polymerizes or cures into a clear stable cross-linked polymer.

The latex polymers of this invention comprise anaqueous dispersion of across-linkable polymer wherein the total solids content of said latexranges from about 45 weight percent up to about 60 weight percent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The vinyl hydrolyzable silanemonomers employed in producing the latex polymer of this invention arethose silanes of the formula wherein X represents a radical selectedfrom the group consisting of gamma-methacryloxypropyl and vinylradicals; wherein each R individually represents a hydrolyzable radicalselected from the group consisting of acetoxy and alkoxy radicals havingfrom 1 to 8 carbon atoms. Illustrative examples of such alkoxy radicalsare methoxy, ethoxy, propoxy, butoxy, isobutoxy, pentoxy, hexoxy, andthe like; alkoxyalkoxy radicals such as methoxymethoxy, ethoxymethox'y,and the like; and alkoxyaryloxy such as ethoxyphenoxy and the like;preferably R is methoxy or ethoxy.

Such silane monomers as well as methods for their preparation are wellknown in the art. Illustrative of the more preferred silanes that can beemployed are for example, vinyltrimethoxysilane, vinyltriethoxysilane,vinyltris (Z-methoxyethoxy) silane,gamma-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, and thelike. The most preferred silane is vinyltrimethoxysilane.

The acrylic esters that can be employed in producing the latex polymerof this invention are the alkyl esters of acrylic acid wherein the alkylgroups are saturated straight or branched chain radicals containing from2 to 20 carbon atoms. Such acrylates as well as methods for theirpreparation are well known in the art. Illustrative examples of suchacrylates that may be mentioned are ethyl acrylate, n-butyl acrylate,tertiary butyl acrylate, isobutyl acrylate, amyl acrylate, ethyl butylacrylate, 2-ethylhexyl acrylate, octylacrylate, nonyl acrylate, decylacrylate, tridecyl acrylate, tetra decyl acrylate, hexadecyl acrylate,octa decyl acrylate, and the like. The most preferred acrylate is2-ethy1hexyl acrylate.

The maleic esters that can be employed in producing the latex polymersof this invention are the alkyl esters of maleic acid, wherein the alkylgroups are saturated straight or branched chain radicals having from 2to 20, preferably 2 to 10, carbon atoms. Such maleates as well asmethods for their preparation are well known in the art. Illustrativeexamples of such maleates that may be mentioned are dibutyl maleate,diethyl maleate, and the like.

The fumaric esters that can be employed in producing the latex polymerof this invention are the alkyl esters of fumaric acid, wherein thealkyl groups are saturated straight or branched chain radicals havingfrom 2 to 20, preferably 2 to 10, carbon atoms. Such fumarates as well.as methods for their preparation are well known in the art.Illustrative examples of such fumarates that may be mentioned arediethyl fumarate, dibutyl fumarate, and the like.

Of course it is to be understood that while it is preferred to employonly single silane and ester'monomers at any one time, if desired, thelatex polymers can be prepared using mixtures of two or more diflFerentsilanes and/ or mixtures of two or more different ester monomers andsuch types of compounds are intended to be covered by the term latexpolymer used herein. t The second essentialmonomer employed in producingthe latex polymers of this invention is vinyl acetate. Ac-

cordingly the polymer of said latex is an interpolymer consistingessentially of (A) a copolymer of (1) a vinyl hydrolyzable silane and(2) vinyl acetate or (B) a terpolymer of (1) a vinyl hydrolyzablesilane, '(2) an ester selected from the group .consistingof acrylicesters, maleic esters or fumaric esters and (3) vinyl acetate. The

most preferred interpolymer of this invention is the interpolymer of avinyl hydrolyzable silane, an acrylic ester and vinyl acetate,especially the interpolymer of vinyl trimethoxysilane,2-ethylhexylacrylate and vinyl acetate.

Other specific interpolymers of this invention that may be mentioned arethe copolymer of vinyltrimethoxysilane and vinyl acetate, the copolymerof vinyltriethoxysilane and vinyl acetate, the copolymer ofvinyltriacetoxysilane and vinyl acetate, the copolymer ofvinyl-tris-(Z-methoxyethoxy)silane and vinyl acetate, the copolymer ofgammamethacryloxypropyltrimethoxysilane and vinyl acetate, theterpolymer of vinyltrimethoxysilane, ethylacrylate, and vinyl acetate,the terpolymer of vinyltriethoxysilane, 2-ethylhexylacrylate and vinylacetate, the terpolymer of vinyltrimethoxysilane, amylacrylate and vinylacetate, the terpolymer of vinyl-tris(2-methoxyethoxy)silane,hexylacrylate and vinyl acetate, the terpolymer of vinyltriacetatesilane, decylacrylate and vinyl acetate, the terpolymer ofvinyltrimet-hoxysilane, tetradecylacrylate and vinyl acetate, theterpolymer of gamma-methacryloxypropyl-trimethoxysilane,2-ethylhexylacrylate and vinyl acetate, the terpolymer ofvinyltrimethoxy silane, octadecylacrylate and vinyl acetate, theterpolymer of vinyltrimethoxysilane, diethyl malonate and vinyl acetate,the terpolymer of vinyltriethoxysilane, dibutyl malonate and vinylacetate, the terpolymer of vinyltrimethoxysilane, diethyl fumarate andvinyl acetate, the terpolymer of vinyltriethoxysilane, dibutyl fumarateand vinyl acetate and the like.

The latex polymers of this invention can be obtained by a process whichcomprises interpolymerizing the monomers in an aqueous dispersionconsisting essentially of (1) a vinyl hydrolyzable silane,

(2) a monomer selected from the class consisting of alkyl acrylates,alkyl maleates, and alkyl fumarates, said alkyl radicals having from 2to 20 carbon atoms, and/or (3) vinyl acetate,

(4) water,

(5) a catalyst, and

(6) a surfactant,

at a temperature ranging from about 20 C. to about 85 0., preferablyfrom about 60 to 85 C.

The silane-vinyl acetate latex polymers of this invention are thosewherein the copolymer consists essentially of about 99 to about 99.5percent by weight of vinyl acetate and about 0.5 to about 1 percent byweight of the silane. Therefore the monomer ratios employed in preparingthese latexes are governed accordingly.

The silane-ester-vinyl acetate latex polymers of this invention arethose wherein the terpolymers consists essentially of about 60(preferably about 85 to about 99 percent by weight of vinyl acetate;about 0.5 to about 39.5 (preferably about 14.5) percent by weight of theester monomer, i.e., the acrylate esters, the maleate esters and thefumarate esters; and about 0.5 to about 5 percent by weight of thesilane. Therefore the monomer ratios employed in preparing these latexesare also governed accordingly.

. Any free radical catalyst or mixtures thereof conventionally known inthe art can be employed. Specific examples of such catalysts areinorganic peroxides such as hydrogen peroxide, ammonium persulfate,potassium persulfate, and the like; organic peroxy catalysts such as thedialkyl peroxides, e.g. diethyl peroxide, diisopropyl peroxide, dilaurylperoxide, dioleyl peroxide, distearyl peroxide, di-(t-butyl) peroxide,di-(t-amyl) peroxide, -dicumyl peroxide, and the like; the alkylhydrogen peroxides such as t-butyl hydroperoxide, t-amyl hydroperoxi-de,cumene hydroperoxide, diisopropyl benzene hydroperoxide; and the like;the symmetrical diacyl peroxides, such as acetyl peroxide, propionylperoxide, lauroyl peroxide, stearoyl peroxide, malonyl peroxide,"succinoyl peroxide, phthaloyl peroxide, benzoyl peroxide and the like;ketone peroxides such as methyl ethyl ketone peroxide,

'4 cyclohexanone peroxide, and the like; the fatty oil acid peroxides,such as cocoanut oil acid peroxides, and the like; the unsymmetrical ormixed diacyl peroxides such as acetyl benzoyl peroxide, propionylbenzoyl peroxide, and the like; the azo compounds, such asazobisisobutyramidine hydrochloride, 2,2, azobis(isobutylronitrile), 2,2-azobis(Z-methylbutyronitrile), 1,1 azobis(1-cyclohexanecarbonitrile),and the like; the disulfide; a redox type catalytic system i.e. acatalyst and a reductant, such as the sulfate-sulfites, thesulfate-sulfoxylate formaldehydes, the peroxy-sulfites, and the like,such as potassium persulfate and sodium metabisulfite, potassiumpersulfate and sodium or zinc sulfoxylate formaldehyde, t-butylhydroperoxide and sodium metabisulfite, potassium persulfate and sodiumthiosulfate, and the like; or mixtures of such catalysts. Obviously onlya catalytic amount of a catalyst need be employed. Generally amounts ofcatalyst ranging from about 0.1 to about 1.5 parts by weight based onparts by Weight of solid polymer in the latex will be sufiicient formost purposes. The most preferred catalyst is potassium persulfate.Redox type catalyst systems are often useful in speeding up the rate ofpolymerization of the monomers and/or in reducing the temperature of thepolymerization process. Of course it is to be understood that thepolymerization of the monomers can be carried out in a closed vessel inan inert atmosphereand under autogenous pressure or under artificiallyinduce pressure or in an open vessel under reflux at atmosphericpressure.

The amount of water present in the system is that amount sufiicient toproduce a latex polymer having "a polymer solids content of from about45 weightpercent up to about 60 weight percent.

Any conventional anionic and nonionic surfactant or mixtures thereof canbe used in the aqueous dispersion of this invention. Such surfactantsare well known in the art and can be found more fully enumerated inSyn-. thetic Detergents by J. W. McCutcheon, published annually byMacNair-Dorland Company, New York. Illustrati've examples of suchsurfactants are the alkali metal salts of rosin acids, alkali metal andammonium salts of long chain alkyl sulfates and sulfonates, the sodiumsalts of sulfonated hydrocarbons, alkaryl sulfonates and the like; thealkylene oxide condensates of long chain alcohols, fatty acids,mercaptans, and the like. Such surfactants are commercially availableunder numerous trade names such as Tergitol compounds, Igepal compounds,Sipex compounds and the like. Among the more preferred surfactants arethe alkoxylated condensates of alkyl phenols such as ethylene oxides ofoctyl and nonyl phenol, alk oxylated condensates of alcohols such asethylene oxides of lauryl alcohol, the alkali metal alkyl sulfonatessuch as sodium lauryl sulfonates, and the like. In some in stances it ispreferred to employ both anionic and nonionic surfactants to helpcontrol particle size of the interpolymer. The amount of surfactantemployed in the instant invention can range from about 0.25 to about 7parts by weight or higher based on 100 parts by weight of solid polymerin the latex.

While not absolutely critical it is generally desirable and highlyrecommended that the aqueous dispersion also contain a small amount of abuffer compound for pH control of the system. Any conventional buiferingagent or mixtures of such agents known in the art can be employed suchas sodium acetate, sodium bicarbonate, and the like. Itis generallydesirable to employ that amount of buffering agent to maintain the pH ofthe aqueous dispersion within the range of about 3.5 to about 6.'Thishelps to prevent hydrolysis of the hydrolyzable groups on the ingredientcompounds. Generally amounts of buffer on the order of about 1.0 partsby weight'or less based on 100 parts by weight of solid polymer in thelatex will be suflicient for-most purposes.

The manner and order in which the monomers and ingredients of the aboveaqueous dispersion are mixed is not critical although it is extremelydesirable to carry out the polymerization of the monomers under constantstirring oragitation. The method employed can be either a batch orcontinuous process and be carried out in one or more steps. For instancethe preferred procedure is continuous method which involves initiallycharging water, surfactant and buffer (when used) to an autoclavefollowed by a batch charge of a portion of the totalmonomer mix andinitiating the polymerization at a-low temperaturewith a small amount ofcatalyst. The polymerization reaction is exothermic and the temperaturerises rapidly. Upon peaking of the temperature (generallyabout 80 C.)the autoclave temperature is lowered about 5 to degrees and controlledby a water bath. Then separate feed streams of (1) a mixture of themonomers and (2) the catalyst are slowly fed (preferably dropwise) tothe reactor, the dispersion being continuouslyagitated. When a redoxcatalytic system is employed it is preferred to add the redox compoundas a separate feed also. After all of the monomer has been added it ispreferred to continue addition of the catalyst for a short post heatingperiod of a few hours to insure maximumpolymerization. The monomer feedtime and post heat time obviously depends only upon the quantity andreactivity of the reactants involved. Formation of the latex; polymercan readily be determined visually by change of color and viscosityanalysis of same e.-g. solution viscosity; total solids, and the like.

, Thelatex polymers of this invention have a wide degree of vutility inthe surfacecoatings field that is well known inthe art. Thejnstantlatex. polymers are particularly unique in that the interpolymerscross-link into a clear stable protective polymeric film coating merelyupon drying, i.e. removal of the water from the latex. The highlycross-linked protective polymeric films derived from said latex polymers are difiicultly soluble in benzene. water and acetone and exhibitexcellent water and solventresistence. In additionwthey are very durableand exhibit a very high degree of scrub resistance and areparticularlyuseful as additives for high pigment volume concentrationpaint formulations and in ceiling tile coat- ;ings When usedunpigmentedthe cross-linked films produce a clear, high gloss coating.Pigmented and unpigmented films may be used as primers, undercoatings ortop coatings on porous or nonporous substrates, such as metal, cement,Wood, wood fibers, mineral fibers, wall board, and the like.

The formation of the crosslinked polymer upon drying of the latexpolymer is readily established by the difiiculty of solubility of thecross-linked polymer film in hydrocarbons, such as benzene and by ananalysis of its properties, e.g. solution viscosity, and the like ascompared to that of the latex interpolymer.

The following examples are illustrative of the present invention and arenot to be regarded as limitative. It is to be understood that all of theparts, percentages and proportions referred to herein and in the amendedclaims are by weight unless otherwise indicated.

, V EXAMP LE 1 A latex polymer was prepared comprising an aqueousdispersion of aninterpolymer consisting essentially of about 94 percentby weight of vinyl acetate, about 5 percent by weight of'2-ethylhexylacrylate and about 1 percent by weight of vinyltrimethoxy silane byadding to a three-liter "glass" bottle having a four-necked separablehead and equipped'twith a dropping funnel 'for monomer addition, athermometer. and a power-driven anchor agitator, and set in a waterlbathfor'heating and cooling an The charge was heated to about 65 C. and 5percent of a monomer premixture consisting of about 752 grams of vinylacetate, about 40 grams of 2-ethylhexyl acrylate and about 8 grams ofvinyltrimethoxysilane were added, and the agitator speed set at such arate that a slight vortex was maintained, along with about 10 percent ofa catalytic premix consisting of 100 grams of water and about 4 grams ofK 8 0}; and with about 10 percent of a reductant premix consisting of 50grams of water and about 4 grams of Na S O When the temperature peaked acontinuous dropwise feed of the rest of the monomer premixture,catalytic premixture and reductant premixture was begun. The balance ofthe monomer feed was added over 4.5 hours and the balance of thecatalyst and reductant over about 5 hours while the temperature wasmaintained at about 70 C. The rate of agitation was increased as thesolid content built up, and slowly decreased during the one hour postcure after final addition of the monomer premixture. The resultant latexpolymer was white, had a total solids content of about 55 percent and alatex viscosity of about 300 centipoises at 25 C. (Brookfield RVTViscometer, #3 spindle, 60 r.p.m.). The latex polymer upon drying(elimination of the water) cross-linked into a clear durable high glossfilm having excellent water and solvent resistance.

EXAMPLE 2 Employing the latex polymer of Example 1, the followingpigmented latex base protective coating composition was prepared.

The above paint formulation was coated onto a plastic plate and dried.The resultant coating exhibited excellent adhesion and scrub resistantproperties when scrubbed with a five percent Lava soap solution on aGardner abrasion tester equipped with a one-pound hog bristle brush.

A controlled comparison was made by preparing the same pigmentedcomposition, except the latex used was a latex of about percent byweight of vinyl acetate and about 5 percent by weight of 2-ethyl hexylacrylate, and subjecting it to the same test procedure. This coatingfree from any silane in the latex exhibited poor scrub resist ance.

EXAMPLE 3 The procedure of Example 1 was repeated employing an aqueouscharge of about 540 grams of water, about 34 grams of a nonionicsurfactant of Tergitol NP-44 (ethylene oxide condensate of alkylphenol),about 6 grams of water and about 4 grams of K S O and and about 1 gramof NaAc-3H O as a buffering agent; a monomer premix of about 750 gramsof vinyl acetate, about 40 grams of 2-ethylhexyl acrylate and about 10grams of vinyltriethoxysilane; a catalyst premix of grams of water 10and about 4 grams of K S O and a reductant premix of 100 grams of waterand about 4 grams of Na S O to produce about a 54 percent total solidscontent of a latex polymer consisting of .an interpolymer of about 93.75percent by weight of vinyl acetate, about 5 percent by weight of2-ethylhexyl acrylate and about 1.25 percent by weight of vinyltriethoxysilane. Upon drying the latex crosslinked into a clear, high gloss film.

7 EXAMPLE 4 Following the procedure of Example 1 a 55 percent totalsolids content of a latex polymer consisting of about 94 percent byweight of vinyl acetate, about percent by weight of 2-ethylhexylacrylate and about 1 percent by weight ofgammamethacryloxypropyltrimethoxy silane was prepared. Upon drying thelatex cross-linked into a clear, high gloss film.

EXAMPLE 5 Following the procedure of Example 1 a 50 to 55 percent totalsolids content of a latex polymer consisting of about 99 percent byweight of vinyl acetate and about 1 percent by weight of vinyltrimethoxysilane was prepared. Upon drying the latex crosslinked into aclear, high gloss film.

Similar latex polymers can be prepared merely by substituting othersilanes for the above vinyltrimethoxysilane monomer, such as,vinyltriethoxysilane, vinyl-tris(2 methoxyethoxy)silane, gammamethacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, and the like.

EXAMPLE 6 About a 55 percent total solids latex polymer consisting of aninterpolymer of about 94 percent by weight of vinyl acetate, about 5percent by weight of Z-ethylhexyl acrylate and about 1 percent by weightof gamma-methacryloxypropyltrimethoxy silane was prepared by followingthe procedure of Example 1, omitting the bulfer. Upon drying the latexcrosslinked into a clear, high gloss film.

Similar latex polymers can be prepared by omitting the nonionicsurfactant, anionic surfactant and/or the reductant, if desired.

EXAMPLE 7 The following latex polymers can be prepared usingconstituents and a procedure similar to that of Example 1 with theexception of" the monomeric components.

TAB LE I Ratio (percent) Percent Latex Interpolymer total solids AVinylacetate/vinyltrimethoxysilane..

B Vinylacetate/ethylacrylate/ vinyltrimethoxysilane.

O Vinylacetate/n-butylacrylate/ vinyltrlethoxysilane.

D Vinylacetate/isobutylacrylate/gamma-methacryloxypropyltrimethoxysilane.

E Vinylacetate/tertiarybutylacrylate/ vinyltriacetoxysilane.

F Vinylacetate/dibutyl maleatel vinyltrimethoxysilane.

G Vinylacetate/diethyl maleate/ vinyltriethoxysilane.

H Vinylacetate/dibutyl tumarate/ vinyltriethoxysilane.

I Vinylacetete/diethyl fumarate/ vinyltrimethoxysilane.

J Vinylacetate/Z-ethylhexylacrylate/ vinyltrimethoxysilane.

K Vinylacetate/amyl acrylate/gazmnamethacryloxypropyltrimethoxysllane.

L Vinylacetate/decylacrylate/ vinyltris-(2-methoxyethoxy)- silane.

M Vinyl acetateloctadecyl acrylate/ vinyltrimethoxysllane.

85:10:& 7 45 weight of an ester selected from the group consisting ofalkyl esters of acrylic acid, alkyl esters of maleic-a'cid and alkylesters of fumaric acid, said alkyl radicals having from 2 to 20 carbonatoms, and about 0.5 to. about 5 percent by weight of a silanehaving'the formula RgSiX. wherein X represents a radical selectedfromthe group consisting of gamma-methacryloxypropyl and vinyl radicals;wherein each R individuallyrepresents a hydrolyzable radical selectedfrom the group consisting of acetoxy and alkoxy radicals having from 1to 8 carbon atoms;and wherein the total solids ofsaid dispersionrangesfrom about 45 to about 60 percent by weight and wherein the aqueousdispersion contains as additional ingredients based on 100 parts byweight of the interpolymer, (a) a catalytic amount of a free radicalcatalyst; (b)'"about 0.25 to about 7 parts by weight of a surfactantselected from the group consisting of an anionic su'rfactant,a nonionicsurfactant, and mixtures thereof, and (c) 'a buffering agent in anamount sufiicientto maintain the pH of the aqueous dispersion Within therange'of about 3.5 to about6.

2. A latex polymer as defined in-claim'l, wherein the interpolymer is aterpolymer consisting essentially of to 99 percent by weight of vinylacetate, 0.5 to 14.5 percent by weight of an alkyl ester of acrylic acidand 0,5 to 5 percent by weight of said silane'. I 1 I 1 3. A latexpolymer as defined in claim 1, wherein-the interpolymer is a terpolymerconsisting essentially of 85 to 99 percent by weightof vinyl acetate,0.5"t'o 14.5'pe'rcent by weight of an alkyl ester of maleicacid'andO.5'-to 5 Percent by weight of said silane.

4. A latex polymer as defined in claiml; whereinthe interpolymer is aterpolymer consisting essentially of to 99 percent by weight'of vinylacetate, 0.5'to 14.5 per cent by weight of an alkyl ester of fumaricacid and 0.5 to 5 percent by weight of said silane'. I I '1 i 5. A latexpolymer is defined in'claim'l, wherein the silane isvinyltrimethoxysilane. A

6. A latex polymer as defined'incla'im 2; wherein the silane isvinyltrimethoxysilane." 1 7. A latex polymer as definedin claim 1,wherein the alkyl ester of acrylic acid is 2-ethylhexyl acrylate.

8. A latex polymer as defined in claim 1, wherein the interpolymerconsists essentially of about '94' pe'rcent"by weight of vinyl acetate,about 5 percent by Weightof-Z- ethylhexyl acrylate and about 1 ercent'by weight of vinyltrimethoxysilane.v f I p 9. A cross-linked polymerobtained by drying a latex Polymer as defined in claim 1. i

10. A cross-linked polymer obtained by drying alatex polymer as definedin claim 6. 1

11. A cross-linked polymer obtained by'drying'a latex polymer as definedin claim 8.

References Cited 1 i UNITED S TAIESI'PAT T' j 3,729,438 4/1973 Plesichet al. 260-49612 2,956,044 10/1960 Merrer 26046.5 3,203,919 8/ 1965.Brachman 260- 296 3,278,476 ,10/1966 Santel1i' 2 60 -2 9.6 3,449,293 6/1969 ,Burzynski et a1. ...V.. 26 0-,,4,6 5

' FOREIGN'PATENTS' 1,149,935 4/19 9 Great Britain 1;.-. 260 29,'6 "TJOSEPH L. SCHOFER, Primary Examiner 5.

I. KIGHT III, Assistant Examiner U.S. C1. xx.

260-465 UA, 78.5 E, 80.71, 80.81;

